From 1 991 to 1 996, seven patients with dialysis underwent open heart surgery, including coronary artery bypass grafting (CABG) in 5 cases, aortic valve replacement in I , and aortic and mitral valve replacement in 1.We evaluated whether open cardiac surgery was safe for the patients with dialysis, and how to manage these patients in the perioperative period. In all patients studied, the dialysis on the day before operation and ECUM during cardiopulmonary bypass were performed. The oxygen index was 264 ± 175 immediately after the arrival to the ICU room and the concentration of serum potassium was within normal limits on the operative day. Water balance was also kept in the minus on the operative day and 1st postoperative day. All patients were extubated on the 1st postoperative day. Dialysis on the day before operation and ECUM during cardiopulmonary bypass are thought to be important for the perioperative management of water balance and adjustment of electrolyte to ensure safer open heart surgery in patients with dialysis.